Base pkg installation on inception VM: Make it compatible with Ubuntu 12.04.

This includes not installing mkpasswd (but keeping it installed for 10.04), and adding "-y" to the PPA addition.
Base packages installation: Install the whois instead of mkpassword packages on Ubuntu != 10.04.
Merge pull request #162 from nand2/master

Base pkg installation on inception VM: Make it compatible with Ubuntu 12.04